Stent graft surgery is a procedure performed for treatment of an abdominal aortic aneurysm or thoracic aortic aneurysm and the like that consists of inserting a tubular fabric and an expandable member contained in a sheath into an exposed blood vessel by making a small incision in the femoral region, continuing to insert until the affected region is reached, and then extending the tubular stent graft fabric with the expandable member and positioning in the blood vessel so as to span normal portions in front of and in back of the affected region so as to repair the affected region from within the blood vessel.
However, stent graft surgery still has numerous problems. An example thereof, although the portion where the stent graft fabric is to be contacted with a vessel wall and fixed thereto is referred to as the landing zone, problems may occur at this landing zone such as leakage of blood (hereinafter to be simply referred to as “endoleakage”) or migration of the stent graft from the landing zone due to inadequate fixation of the stent graft fabric (hereinafter to be simply referred to as “migration”).
An example of one mode of endoleakage is a phenomenon in which blood flows into an aneurysm from a gap between the stent graft and a blood vessel. This has been indicated to be caused by oversizing or looseness of the fabric at the landing zone where closest contact is to be made with the blood vessel.
In general, a tubular stent graft fabric having a diameter roughly 20% larger than the diameter of blood vessel in the landing zone of a patient is used in the clinical setting. Since a normal blood vessel wall expands in diameter by about 10% due to its flexibility, the stent graft fabric, which has ample size relative to blood vessel diameter, is pushed against the blood vessel wall and fixed in position. As a result, as is described in Patent Documents 1 and 2 indicated below, the fabric may become loose after being expanded within the blood vessel and may end up sticking up inside the blood vessel in the manner of a sail, thereby enabling blood to be guided to the inside of the sail and resulting in the occurrence of endoleakage.
Although stent grafts are pushed into a blood vessel from the sheath and pushed apart with the expandable member, the status of the fabric following fixation in the landing zone cannot be confirmed by X-ray.
In addition, as was previously described, fixation of the stent graft is dependent upon pressure applied from lumen towards the vessel inner wall by the expandable member. However, in the case of a diseased vessel wall, inner diameter gradually increases, and pressure applied to the vessel wall at the point that inner diameter has exceeded the inner diameter of the stent graft, namely, the strength that enables fixation of the stent graft, is lost. Therefore, although a fixation method has been employed by which narrow hooks attached to the expandable member are driven into the vessel wall, this is unable to completely prevent migration.
Fixation of a stent graft must be maintained throughout the life of the patient. Thus, it is necessary to provide means of continuous fixation of the fabric even if the inner diameter of a diseased blood vessel wall has expanded.
As has been described above, the prior art has not yet solved the problems of endoleakage and migration.